Enhanced Interface Stability of Polymer Electrolytes Using Organic Cage-Type Cucurbit[6]uril for Lithium Metal Batteries

Abstract

Safety, energy density and cycling life are believed to the most three urgent concerns to develop next-generation high-performance lithium ion batteries. Lithium metal anode is attractive owing to the extremely high theoretical specific capacity and the lowest negative electrochemical potential. However, the use of metallic lithium anode has been limited by the poor interface stability with the electrolyte along with the occurrence of dendrite growth. Here, we report a self-standing flexible composite polymer electrolyte (CPE) incorporated with organic robust cage-type cucurbit[6]uril (CB[6]) prepared by solvent-free hot-pressing method. Poly(ethylene oxide)-Lithium bis(trifluoromethanesulfonyl)imide with 35 wt% CB[6] composite electrolyte exhibits a wide electrochemical window at 55°C (4.7 V vs. Li+/Li) and high thermal stability (380°C). The interface stability with lithium metal anode is significantly enhanced by the addition of CB[6]. At 0.5 C rate under operation temperature of 55°C, the LiFePO4|CPE|Li battery demonstrates excellent cycling performance with high capacity retention of 99.8% at 100th cycle and 86.5% at 200th cycle, which indicates that such CPE membranes are able to present stable electrode/electrolyte interface and inhibit lithium dendrite growth for achieving high-safety all-solid-state batteries.